Canonical Wnt signaling is particularly important for differentiation of human mesenchymal stem cells into osteoblast. MicroRNAs (miRNAs) also play an essential role in regulating cell differentiation. However, the role of miRNAs in osteoblast differentiation remains poorly understood. Here we found that the expression of miR-27 was increased during hFOB1.19 cells differentiation. Moreover, ectopic expression of miR-27 promoted hFOB1.19 cells differentiation, whereas its repression was sufficient to inhibit cell differentiation. Western blot analysis showed that the expression level of miR-27 was positively correlated with that of p-catenin, a key protein in Wnt signaling. Further, we verified that miR-27 directly targeted and inhibited adenomatous polyposis coli (APC) gene expression, and activated Wnt signaling through accumulation of p-catenin. This study suggests miR-27 is an important mediator of osteoblast differentiation, thus offering a new target for the development of preventive or therapeutic agents against osteogenic disorders. (C) 2010 Published by Elsevier Inc.